MINERALS AND CRYSTALS 183 



candy (crystals of sugar) and alum, can be bought at 

 the chemists, if it is not possible to procure minerals. 



A striking example of crystals sharing space can be 

 obtained by dissolving together in a glass of hot water 

 one ounce of potassium bichlorate and one ounce of copper 

 sulphate. If a straw or a string is put in the glass the 

 different crystals will form upon it and show quite plainly. 



As these chemicals are poisonous it is not advisable 

 for the children to handle them, but they should see the 

 teacher's results. They could dissolve alum in hot water 

 and watch the crystals form as it cools about a straw or 

 small stick resting in the glass. Always make a saturated 

 solution, that is, make the Water dissolve as much alum 

 as it will hold, when crystals are desired. 



Where possible, the children should be taken to a 

 museum by their teacher or parents. They will never 

 forget the surprising shapes or the superb colors of the 

 crystals which they will see there, especially when the 

 visit is made in connection with this lesson. 



Hand Work. 



A list of minerals and crystals each pupil knows is to 

 be entered in the space left for the purpose. 



Use the blank page on the leaflet for some original 

 work. The children may, for example, draw the forms of 

 different crystals they have seen, or insert pictures of 

 them, or write an account of their experiment with alum. 



OPENING TALK 



The object lesson which the specimens of crystals will 

 furnish is the best introduction to the story, for when 

 they see crystals the children will be anxious to learn 

 how they are formed. 



